Rigsy

"Rigsy" was the self-appointed pseudonym of Christopher Riggins, a graffiti artist from Bristol, whose criminal activity saw him sentenced to community service. He helped Clara Oswald fight the Boneless. Rigsy's aunt was one of many people in Bristol who had been experimented upon by the Boneless. Rigsy attempted a self-sacrifice to ram an empty subway commuter train into them, which needed a person to hold the dead man's lever in place so it would remain in operation. Clara, however, used a headband to restrain the lever instead and let the train run with nobody inside, saving Rigsy from an unnecessary demise. Rigsy later used his artistic skills to create a fake door, which tricked the Boneless into charging the TARDIS because the door never existed in 3D, and the Boneless tried making his art 3D.

Having moved to London, Rigsy now has a fiancee Jen and baby girl Lucy. However, he calls the Doctor and Clara in the TARDIS when he wakes up one morning to find a countdown 'tattoo' on the back of his neck. The trio investigate and discover a secret "Trap Street" hidden away in London. Accused of being a murderer, it eventually transpires that Rigsy was set up by Ashildr - now the street's mayor/protector - in order to get the Doctor there so he could be caught and transmatted to someplace else. However, Clara had unwittingly taken on the death sentence from Rigsy without realising the contract could not be broken by her, and so she instead "faces the Raven" ...

Rigsy honours her with a graffiti display across the TARDIS, which has been left on its own ...

"Flatline" biography adapted from the TARDIS Data Core article, licensed under CC-BY-SA